Microsoft Excel comes with a lot of built-in functionality that doesn't restrict you to comparing data in two columns using only one method.

Creating a list of duplicate values that’s separate from the data source is easier than ever thanks to Microsoft Excel's FILTER() function.

Combine INDEX and MATCH: Use MATCH to find the row or column number and INDEX to retrieve the value at that position.

SUM is the spreadsheet equivalent of an open invite: it welcomes everything into the total, whether it belongs there or not.